Sodium acid pyrophosphate
M. F.: Na2H2P2O7
M. W. : 221.94
Physical properties: Monoclinic, white crystalline powder. Density 1.86. Practically insoluble in alcohol, soluble in water. Hydrolyzes to orthophosphate on heating in acid medium. Hygroscopic, forms hexahydrate in damp air. Decomposes to metaphosphate at above 220°C
Usage: Used as rapid ferment agent, quality improver in food industry. Applied to acid component of synthetic swelling agent, such as, bread, cake. Builted with other phosphates can be applied to water retention of meat product, such as canned meat, cooked ham, meat can and instant noodles.

Diffnation:
Disodium pyrophosphate or sodium acid pyrophosphate is an inorganic compound consisting of sodium cations and pyrophosphate anion. It is a white, water-soluble solid that is serves buffering and chelating agent, with many applications in the food industry.
SAPP is usually used in very sweet cakes which mask the off-taste. It is used in canned seafood to maintain color and reduce purge during retorting. Retorting achieves microbial stability with heat.
It is an acid source for
Specification:
Appearance: White powder;
Main content(as Na2H2P2O7): 95% min;
Insoluble matter in water: 1.0% max;
Heavy Metal(AS Pb): 10ppm max.;
AS%:0.0003max;
Pb: 2ppm max.;
F: 50PPM max.;
PH VALUE(1% aqueous solution): 3.5-4.5
Particle size distribution (mesh)
Through 80 mesh sieve, %   95min
Through 200mesh sieve, %   90min
Packing: It is packed with ployethylene bags as line-r , and a woven bag as the outer layer. The net weight of each bag is 25kg.